Altitude indicator system



March 18, 195 3 w. PIKE 2,589,860

ALTITUDE INDICATOR SYSTEM Filed Dec. 10, 1945 FIG. 1

BEACON BEACON RECEIVER M'XER TRANSMITTER ,ls ALTITUDE GODER MULTIVIBRATOR PEAKE MIXER,

wvnvron BEUHRING W. PIKE WW .9. Me

ATTORNEY Patented Mar. 18, 1952 p LT1TU1)EinnroA'ron SYSTEM Beuhring W. Pike, Watertown, Mass, assignor,

by 'mesne assignments, to-the United States of America as represented by the Secretary of War Application December 10,1945, Serial No. 634,080 1 Claim. (01. 343'- This invention relates generally to electrical apparatus and more particularly to radio responder beacons in aircraft.

In the control of air traific by the use of a radio object detection apparatus on the ground, it is particularly desirable to provide continuous indication of the altitude of the aircraft being controlled. It is an object of this invention to provide such continuous altitude indication by means of a beacon carried by each such aircraft.

Other objects, features and advantages of this invention will suggest themselves to those skilled in the art and will become apparent from the following description of the invention taken in connection with the accompanying drawing in which:

Fig. 1 is a block diagram of a radio responder beacon embodying the principles of this invention; and

Fig. 2 is a schematic Wiring diagram of this invention.

Reference is now made more particularly to Fig. 1 in which beacon receiver H is connected to antenna I2 and to altitude coder [3 and mixer 14. Altitude coder I3 is connected to altimeter I6 and mixer i l, and beacon transmitter l1 connects to mixer I4 and antenna 18.

Beacon receiver I 1 receives radio-frequency interrogating pulses from the radio object detece tion apparatus on the ground, through the medium of antenna i2, and supplies video pulses to mixer l4 and to altitude coder l3. Altitude coder 13 produces a second video pulse which is delayed after the pulse from receiver H by an amount determined by altimeter l6. Altitude coder I 3, which will be described below in greater detail, supplies the delayed pulse to mixer 14, which may be any of several mixers well known to those skilled in the art. Both the original pulses from receiver H and the delayed pulses from altitude coder l3 are applied to transmitter ll, causing it to emit pairs of pulses of radio-frequency en- 2 22, of the type shown and described in the application by Britton Chance, Serial No. 512,931, filed December 4, 1943, Patent No. 2,562,660, granted July 31, 1951, followed by a derivative circuit or peaker 23, which is well known in the art. As described in the application cited, multivibrator 22 has a stable condition of equilibrium in which tube 24 conducts, and an unstable condition in which tube 26 conducts. The unstable period is initiated by the positive pulse from beacon receiver I l, which is applied to the grid of tube 26, and the duration of the unstable period is linearly propostional to the D. C. potential on the grid of tube 26. Accordingly, potentiometer 2'! is arranged to control the D. C. grid potential of tube 26, the sliding contact of potentiometer 21 being driven by altimeter l 6. Altimeter l 6 is here indicated as being of the aneroid type, although it may be replaced by any altimeter capable of driving potentiometer 21.

The waveform of the voltage appearing at the grid of tube 24 is a negative voltage pulse of approximately rectangular shape, the leading edge of which coincides in time with the reception of a pulse by beacon receiver H, and the duration of which is proportional to the altitude. This voltage pulse is applied to peaker circuit 23, so that the voltage applied to mixer It consists of a short, sharp negative pulse coinciding with the leading edge of the rectangular pulse, followed by a short, sharp positive pulse coinciding with the trailing edge of the rectangular pulse. Only the positive pulse is transmitted by diode 28 to terminal 29, and since the received pulse is similarly transmitted by diode 3i the output voltage at terminal 29 consists of two successive positive voltage pulses separated in time by an amount ergy through the medium of antenna 13, the

pulses of each pair being separated in time by an amount proportional to the altitude of the aircraft.

Referring now more particularly to Fig. 2'for an illustration of the altitude coder 13, the pulses proportional to the altitude of the aircraft.

As previously described, the beacon transmitter H is caused by these pulses to emit corresponding pulses of R. F. energy. When received by the radio object detection apparatus on the ground, these two pulses produce separate traces on the indicating means, so that the operator receives a visual indication of the aircraft altitude, as well as the usual indication of range and azimuth.

Whi1e there has been described what is at present considered to be the preferred embodiment from beacon receiver H are applied at terminal.

Altitude coder 13 may include any conven of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scribed, this means consists of a multivibrator scope of the invention.

The invention claimed is: An airborne radio responder beacon, including:

receiving means receptive of at leastohe interrogating pulse of radio frequency energy; means for determining the altitude of said airborne beacon; multivibrator means having its input connected to the output of said receiving means, said multivibrator means producing a square wave whenever an energy pulse is coupled to its input; means for difierentiating the output of said multivibrator means to produce a delayed output pulse synchronous with the trailing edge of said square Wave; transmitting means, having its input coupled to the outputs of both said receiving means and said differentiating means, for transmitting both said interrogating pulse and said delayed pulse; and means coupled between said altitude determining means and said multivibrator means, for varying the duration of said square wave in response to the variations in altitude of said airborne beacon, thereby varywith said variations in altitude of said beacon. BEUHRING W. PIKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 7 Date 2,252,083 Luck Aug. 12, 1941 2,283,919 Diamond et a1. May 26, 1942 2,287,786 Diamond et al June 30, 1942 2,415,359 Loughlin Feb. 4, 1947 2,448,016 Busignies Aug. 31, 1948 2,479,954 Moore Aug. 23, 1949 2,495,737 Labin et al Jan. 31, 1950 

